Condensed Consolidated Statements of Comprehensive Income (Parenthetical) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Statement of Comprehensive Income [Abstract]    
Unrealized gain (loss) on investments, tax $ 16 $ (14)
Changes in benefit plan accounts, tax $ 581 $ 678